Quote Originally Posted by Mouzafphaerre
-
I've never heard or seen by feet; neither of my bigg-αß dictionaries (Collins Cobuild and Grolier Webster) include it either, while both of them have on foot.
-
You are right. It is 'by foot' and 'on foot'. It does implicate a difference. I think I am close with the 'to do' and 'have done', but it is just a hunch.